1. Field of the Invention
The present invention relates to a reflective optical encoder having a resin-made code plate.
2. Description of the Related Art
An optical encoder is connected to a rotation axis, etc., of a motor, and is used to detect the rotational position and velocity of the rotation axis. As an example of such an encoder, JP 2004-325231 A discloses an optical encoder having a light emitting unit positioned near one side of a resin-made code plate and a light receiving unit positioned near the other side of the code plate, wherein light from the light emitting unit passes through the code plate and is received by the light receiving unit.
In the encoder as disclosed in JP 2004-325231 A, the light emitting unit and the light receiving unit are positioned near the opposed sides of the code plate. Therefore, an axial dimension of the encoder is relatively large. In this regard, for example, JP H11-287671 A (FIGS. 12 to 15) discloses an optical encoder having a light emitting unit and a light receiving unit positioned near the same side of a code plate, wherein light from the light emitting unit is reflected by the code plate and is received by the light receiving unit.
As in the encoder as disclosed in JP 2004-325231 A, when the light emitting unit and the light receiving unit are positioned near the opposed sides of the code plate, the axial dimension of the encoder is relatively large.